Django: How to populate order form fields (First Name, Last Name, Phone) if user is already registered and logged in?

Question

Django

There is an order model (in models.py):

class Order(models.Model):
    user = models.ForeignKey(settings.AUTH_USER_MODEL, on_delete=models.CASCADE,)
    first_name = models.CharField(max_length=50, verbose_name="Заказчик")
    last_name = models.CharField(max_length=50, blank=True)
    phone = models.CharField(max_length=20)
    address = models.CharField(max_length=255, blank=True)
    date = models.DateTimeField(auto_now_add=True, verbose_name="Дата заказа")
    delivery_type = models.CharField(max_length=40, choices=(('self','Самовывоз'),('delivery','Доставка')), default='self', verbose_name="Тип доставки")
    delivery_date = models.DateField(default=get_tomorrow())
    comments = models.TextField(blank=True)
    status = models.CharField(max_length=100, choices=ORDER_STATUS_CHOICES, default='accepted', verbose_name="Статус")
    total_cost = models.DecimalField(max_digits=9, decimal_places=2, default=0.00, verbose_name="Итоговая стоимость")
    discount = models.DecimalField(max_digits=5, decimal_places=2, default=0.00)

    class Meta:
        verbose_name = "Заказ"
        verbose_name_plural = "Заказы"

    def __str__(self):
        return "Заказ #{0}".format(str(self.id))

As you can see, it uses users who are registered in the system. If the user is not registered, then he will not get to the checkout page.
There is a form (in forms.py):

class OrderForm(forms.ModelForm):
    class Meta:
        model = Order
        fields = ['first_name', 'last_name', 'phone', 'delivery_type', 'delivery_date', 'address', 'comments']
        labels = {
            'first_name': 'Имя *',
            'last_name': 'Фамилия',
            'phone': 'Контактный телефон *',
            'delivery_type': 'Способ получения',
            'delivery_date': 'Дата доставки',
            'address': 'Адрес доставки',
            'comments': 'Комментарии к заказу',
        }
        help_texts = {
            'phone': '* Пожалуйста, указывайте реальный номер телефона, по которому с Вами можно связаться',
            'address': '* Обязательно указывайте город!',
            'delivery_date': '! Доставка производится не раньше, чем на следущий день, после оформления заказа. Менеджер с Вами предварительно свяжется!',
        }
        widgets = {
            'delivery_date': forms.SelectDateWidget(),
        }

The form is generated automatically using the django-bootstrap3 extension and in the template the code looks like this:

<div class="col-xs-offset-1 col-xs-8">
<form method='POST' action='{% url "make_order" %}' class="form-horizontal"> {% csrf_token %}
    {% bootstrap_form form show_label=False layout='horizontal' %}
    {% bootstrap_button "Отправить заказ" icon="ok" button_type="submit" button_class="btn-success" extra_classes="pull-right" %}
</form>
</div>

And in the browser it’s like this:

if you select delivery (additional fields will open, I did it through Ajax), but you shouldn’t be distracted by this.

So it turns out that every time an already logged-in user has to Specify the first name, last name and phone number. But they are in the profile.

What should I add where (ideally to the forms.py file) so that these fields are filled in automatically?